Multi-piece fiber optic component and manufacturing technique

ABSTRACT

An apparatus for use in a commercial fiber optic connector is made up of an assembly of a set of slices. Each of the slices having multiple through holes of a specified arrangement. At least some of the through holes on any two adjoining slices are aligned with respect to each other so as to define a conduit between them. A transmission medium is within the holes. A method of making a fiber optic connector adapted to receive a fiber bearing unit is also described. The method involves coupling at least two high precision pieces together, the at least two high precision pieces having holes configured with an optical medium inserted therein after the coupling and cured to form a waveguide structure, coupling the at least two high precision pieces to a low precision piece to form a unit, and housing the unit within a fiber optic connector housing.

This is of co-pending application Ser. No. 09/896,196, filed Jun. 29,2001.

FIELD OF THE INVENTION

This invention relates to components and processes for fiber opticrelated component fabrication. More particularly, the invention relatesto fabrication of fiber optic connectors and components used inconjunction therewith.

BACKGROUND OF THE INVENTION

Optical Fibers in commercial systems have been traditionally held byusing a combination of pieces.

A connector assembly 100, such as shown in FIG. 1 as an exploded view isused to attach various fiber pieces (or fiber pieces and modules)together. A ferrule 102 is the part of the connector 100 into which thefibers 104 themselves are inserted before the ferrule 102 is insertedinto the overall connector itself. The ferrule 102 is a ‘high-precision’piece of the assembly 100. It holds the fiber(s) 104 in a preciseposition and ensures that when two connector pieces are attached, thatthe fibers in the two pieces are held in accurate alignment. Theremainder of the connector 106 is ‘low precision’ relative to theferrule 102.

In the multi-fiber connectors available today, most of the connectionsare for fiber arrays of 2 or more fibers, such as shown in U.S. Pat. No.5,214,730, up to arrays of 1×12 (although some commercial 2×12configurations have been tried). The connectors employed are referred toby various names depending upon who makes them. In 1×2 arrays,connectors are referred to as ST, LC, MT-RJ connectors while for 1×12arrays the connectors are referred to as MTP®, MPO, MPX and SMCconnectors, among others. In the 1×12 or 2×12 area, all of the variousconnectors use a common type of ferrule commercially available from,among others, US Conec Ltd. and Alcoa Fujikura Ltd. In addition,commercial connectors for small arrays (less than 12) fibers have alsobeen proposed, for example, in U.S. Pat. No. 5,743,785.

Fiber holding pieces, such as ferrules 102, can be made by moldingplastic or epoxy pieces containing holes 108 into which optical fibers104 can be inserted. Fibers must be able to be centered in each holeprecisely and repeatably.

When an array of holes is made in a material for holding optical fibers,there are two aspects which need to be controlled. The spacing betweenholes (the “pitch” of the holes) and the diameter of each hole. Bothhave some margin of error due to the inherent inaccuracies of thefabrication techniques. If inaccuracies introduce errors in either (orboth) pitch or size that are too large, then the fibers can be insertedat an angle or will not be positioned correctly in the ferrule. Ineither case, this negatively affects the ability to couple lightefficiently, if at all, from one bundle to another or from an optical oropto-electronic component to a fiber bundle. If the hole pitch isinaccurate, then fibers from one bundle will not line up well withfibers of another bundle. However, even if the center-to-center pitch ofthe holes is very accurate, because the hole diameter is larger than thefiber (and each hole likely varies across an array) each fiber need notbe in the exact same place in the hole as the other fibers in theirholes, then that can cause misalignment, leading to inefficiencies orunacceptable losses. For example, if each of the holes in a ferrulepiece was accurate to within 4 microns, then adjacent fibers could beoff in pitch by up to 4 microns, since one fiber could be pushed to oneside by 2 microns and the adjacent fiber could be pushed in the otherdirection by 2 microns. While this may be acceptable for multi-modefibers, for single mode fibers this would be a huge offset that couldmake connections unacceptable or impossible.

In addition, fibers should generally not be placed in a hole at an angleor, if inserted at an angle, the particular angle should be specificallycontrolled.

FIG. 2 shows an example ferrule hole 200 and fiber 202. The innercircle, represents an actual fiber 202 while the outer circle,represents the hole 200 in the ferrule. As shown, the difference insizes is not to scale but is exaggerated for purposes of illustration.Nevertheless, in actuality, the ferrule hole 200 must be larger than thefiber 202 by enough of a margin to allow for easy insertion—ultra-tighttolerances can not be effectively used. While the fiber 202 shouldideally be centered with respect to the hole 200, as can be seen in FIG.3, any individual fiber 202 could also be pushed in any hole 200 tosomewhere else in the hole, for example, either the left or right edge(or any other edge) where it would not be centered within the hole 200.Thus, even if the ferrule has an accurate pitch “P”, between holecenters 206, adjacent fibers 202 in an array may have an incorrect pitch“P+2ΔP” due to the offset P between the center 206 of each hole 200 andwhere the fiber 202 lies within the hole 200, in this case, causing anincorrect pitch of P plus 2 times the individual offset ΔP in each hole.

The 1×12 and 2×12 ferrule technology currently in commercial use isbased upon a glass filled epoxy resin (a high-performance plastic) whichis fabricated using a common plastic molding technique called transfermolding. Today, ferrules molded out of epoxies or plastics can be madeto the necessary tolerances for multimode fibers, but special care mustbe taken during fabrication. Plastic molding technology is very processsensitive and molds having the requisite precision are extremelydifficult to make. Even so, yields tend to be poor due to the inherentmanufacturing process errors that occur in plastics molding. Since thetolerances on these pieces must be very accurate (on the order of about1 to 2 micrometers), high yield manufacture is difficult. As a result,the cost of terminating fiber bundles into these connectors can be quiteexpensive, running hundreds of dollars per side. In addition, theprocess is not scalable to larger numbers of fibers (particularly 30 ormore) because of inaccuracies and yield issues associated with moldingtechnology and reliable production of ferrules for similar numbers ofsingle mode fibers is even more difficult.

There has been an increasing need among users in the fiberoptic fieldfor larger groups of fibers, so demand for connectors to handle thesegroups has been increasing as well. As a result, creation of connectorsfor larger arrays, such as 5×12, have been attempted. One manufactureris known to have made a 5×12 connector array, but achieved such pooryields that they deemed an array of that size unmanufacturable.Moreover, the cost of producing the pieces resulted in their being soldfor $500 each, due to poor yield, and the mold for producing the pieceswas destroyed during the process.

The problem is that in plastic molding pieces for holding higher fibercounts in small spaces results in less structural integrity for themolded piece. As such, the prior art has been forced to do withoutcommercial connectors for such large arrays, because 5×12 arrays can notbe reliably created and commercial connectors for larger format arrays(e.g. even a 6×12) are considered prohibitively difficult to evenattempt.

The ferrule area is very small, since ferrules for the above MTP, MPO,MPX or SMC connectors are about 0.07″ high, 0.3″ wide and 0.4″ deep, somolding or machining of features in the ferrules of the sizes requiredto hold multiple optical fibers (which typically have about a 125 microndiameter for a multimode fiber and a 9 micron diameter core for a singlemode fiber) is very difficult. Since single mode fibers have an evensmaller diameter than multimode fibers, molding or machining ferrules toaccommodate large arrays of single mode fibers is currently, for allpractical purposes, impossible—particularly on a cost effectivecommercially viable scale.

Additionally, making ferrules for arrays is made more difficult due toprocess variations during production because, as the holes approach theedge of the ferrule, the structural integrity of the walls decreasecausing parts to have poor tolerance at the periphery, become overlyfragile causing component collapse in some cases, or prohibiting removalof material from the inside of the piece that impedes or prevents fiberinsertion.

Some have attempted to make two-dimensional fiber bundle arrays for bycreating a dense packing of fibers together, for example, as describedin U.S. Pat. No. 5,473,716, and K. Koyabu, F. Ohira, T. Yamamoto,“Fabrication of Two-Dimensional Fiber Arrays Using Microferrules” IEEETransactions on Components, Packaging and Manufacturing Technology-PartC, Vol 21, No 1, January 1998. However, these attempts have not yieldeda solution, particularly for the types of connectors mentioned above,because the inaccuracies of fiber production result in diameters offibers which fluctuate within a 2 micron range (i.e. plus or minus 1micron). Hence if 12 fibers are stacked in a row, there could be as muchas 12 microns of inaccuracy in fiber alignment. Even with multi-modefibers (the best of which use 50 micron cores), a misalignment of 12microns will cause unacceptable light loss for most applications. Forsingle mode fibers, which typically have 9 micron diameter cores, a 7 to12 micron misalignment could mean that, irrespective of the alignment ofthe fiber at one end of the row, entire fibers at or near the other endof the row could receive no light whatsoever. For two-dimensional fiberarrays, the problem is even worse because the inaccuracy of the fiber isnot limited to one direction. Thus, for example with a 16×16 array, aplus or minus 1 micron inaccuracy could result in fiber misalignments byup to 23 microns or more. Compounding the problem is the further factthat fiber inaccuracies stated as plus or minus 1 micron do not meanthat fiber manufacturers guarantee that the fiber will be inaccurate byno more than 1 micron. Rather, the inaccuracy statement represents astandard deviation error range. This means that most of the fiber shouldonly be that inaccurate. Individual fibers, or portions thereof, couldhave larger inaccuracies due to statistical variations.

As a result, the larger the number of fibers, the more likely a problemdue to fiber inaccuracy will occur because, for example, using the 16×16array above, the array would have 256 times the chance (because thereare 16×16=256 fibers) of having at least one of these statisticallyanomalous fibers in the group.

Others have attempted to align two dimensional arrays of fibers (e.g.4×4 arrays) in a research setting, but none have applied theirtechniques to conventional connector technologies. Moreover, thetechniques are not suitable or readily adaptable for high yield, lowcost, mass production as demanded by the industry. For example, somegroups have examined the use of micromachined pieces made out ofpolyimide as described in J. Sasian, R. Novotny, M. Beckman, S. Walker,M. Wojcik, S. Hinterlong, “Fabrication of fiber bundle arrays forfree-space photonic switching systems,” Optical Engineering, Vol 33, #9pp. 2979-2985 September 1994.

Others have attempted to use silicon as a ferrule for precisely holdingfiber bundle arrays since silicon can be manufactured with very highprecision (better than 1 micron) and techniques for processing ofsilicon for high yield is, in general, well understood.

Early attempts at silicon machining for two-dimensional array fiberplacement were performed with some limited success and one-dimensionalfiber arrays, using fibers placed in V-Grooves etched into a piece ofsilicon, have been created, for example, as shown in FIG. 4A. Theapproach used the silicon pieces to hold the fibers but no attempt wasmade to integrate such an arrangement into a commercial connector.

Other groups took the V-Groove approach of FIG. 4A and performed anexperiment where they stacked two of pieces together FIG. 4B forinsertion into a connector. This resulted in a minimal array with tworows of fibers, as described in H. Kosaka, M. Kajita, M. Yamada, Y.Sugimoto, “Plastic-Based Receptacle-Type VCSEL-Array modules with Oneand Two Dimensions Fabricated using the self-Alignment MountingTechnique,” IEEE Electronic Components and Technology Conference, pp.382-390 (1997), but the technique was not scalable to larger formattwo-dimensional arrays, such as shown in FIG. 4C.

Still other groups looked at holding larger format two-dimensionalarrays using silicon pieces machined using wet-etching techniques, asdescribed in G. Proudley, C. Stace, H. White, “Fabrication of twodimensional fiber optic arrays for an optical crossbar switch,” OpticalEngineering, Vol 33, #2, pp. 627-635, February 1994.

While these silicon pieces were able to hold fibers, they were notdesigned to be, and could not readily be, used with existing ferrule orconnector technology. Moreover, they could not be used for single modefibers with any accuracy.

Thus, none of the above attempts have provided a viable solution to theproblem of how to effectively create a large format fiber array which:allows for high precision holding of large arrays of fibers, especiallysingle mode fibers, is compatible with current commercially usedconnectors that attach two fiber bundles to each other or one fiberbundle to a component containing an array of optical devices, such aslasers and/or detectors, and that allows for easy fiber termination in arapid fashion at low production cost.

In addition, because of the above problems, there is presently no largeformat ferrule apparatus that can maintain fibers at a low angle, or ata precisely specified angle, for good optical coupling.

Collimating arrays are conceptually arrays of pipes for light. Massproduction of collimating arrays for commercial applications has largelybeen dominated by the digital photographic camera and digital videocamera world. These applications typically use a device called a“faceplate”, which is a multi-fiber assembly used to direct light ontooptical detectors used for imaging. Since, for cameras, effectiveimaging requires the maximum amount of light reach the detectors, afaceplate will have several fibers per individual detector. In fact, inthe most desirable faceplates, the number of optical fibers exceeds thenumber of optical detectors by many times. Thus, light being directed toa single detector in such a camera passes through multiple opticalfibers arranged in parallel, and a camera has one detector per pixel.For imaging systems like cameras, this collimating technique issufficient to accomplish its purpose. However, when dealing with opticalcommunication systems, faceplates can not be used because the light lossresulting from such a collimating arrangement is significant. Thefaceplate technique (sometimes also referred to as oversampling) is alsoincompatible with the use of single mode fibers or lasers (which arehighly desirable for use in high speed, long distance datatransmission). Hence, the collimating technique of using a faceplate,such as made for use in cameras, is an unworkable approach foropto-electronic communication devices.

As noted above, for one-dimensional optical device arrays, attempts havebeen made to create collimators by using a piece of silicon wafer, intowhich V-Grooves are etched, and laying the fibers into the V-Grooves asshown in FIG. 4A. This is an operational approach for forming aone-dimensional array that is unsuitable for mass production.

Other groups have attempted to stack multiple V-Groove arrays on top ofone another (FIGS. 4 b, 4 c) to create a larger collimating element.Unfortunately, the accuracy of stacking in the second dimension islimited by the accuracy of the thickness of the individual wafers, bothon an absolute basis and on a relative basis, due to thicknessvariations over the area of the wafer. In addition, the stacked V-Groovetechnique requires such accuracy that individual stacks must beindividually built up one at a time; a costly and inefficient process.

Presently, there are also no inexpensive two dimensional opticalwaveguide combiners available for commercial applications or that can beused with a fiber array. In some cases, optical fibers are twist fusedto form a 2 to 1 “Y” branch, for example, for coupling a pumping laserto a single, signal carrying, fiber. For one-dimensional arrays ofdevices, Y branches have been created on the surface of a wafer bypatterning, using lithographic techniques, to form waveguides. Thistechnique provides robust control for a one-dimensional array, butcannot be extended into two dimensions since it is inherently a planarprocess.

SUMMARY OF THE INVENTION

We have created a processing and fabrication technique for multi-pieceferrule technology that satisfies the different needs in the art. Byapplying the teachings herein, ferrules that are designed for holdinglarge format arrays of multimode or single mode optical fibers can becreated. The processing and fabrication strategies enable low-cost fibertermination in a ferrule (i.e. the fiber bundles can be inserted in ahigh yield and rapid process which keeps costs of assembly minimal). Inaddition, if desired, fibers can be placed in the connector straight(i.e. not at an angle), or at a pre-determined angle to minimize opticalloss resulting from the connector.

Advantageously, the technique is scalable, permitting subsequentgenerations of devices to have greater and greater numbers of fibers andallowing common designs to be used for both multimode and single modefibers.

By using our approach, connectors that connect multi-fiber bundles tocomponents, boards, or one another, can be made at a lower materialcost, in a highly accurate manner, on a production scale previouslyunavailable and do so in a manner that is not overly labor intensive.

The approach further allows manufacture of easy-insertion, high yieldcomponents that, in combination, provide a precision of fiber placementaccuracy that is higher than the precision of any one individual piecealone. The use of this approach allows the fabrication of individualcomponents, using batch manufacturing low-cost processes, which, bythemselves, might only be accurate enough to hold multi-mode fibers but,when the components are combined, provide accuracies compatible withholding single mode fibers, whether individual fibers, or aone-dimensional or two-dimensional fiber arrays.

Moreover, the technique for creating high precision components allowsthe creation of optical elements that provide additional benefitsbecause they can be fit into a connector, may or may not hold opticalfibers, and add a third dimension of freedom. This enables theconstruction of not only fiber holding elements, but also collimatorarrays, Y branch, two-dimensional waveguides, and three-dimensionaloptical integrated circuits.

One aspect of the invention involves an apparatus for use in acommercial fiber optic connector is made up of an assembly of a set ofslices. Each of the slices having multiple through holes of a specifiedarrangement. At least some of the through holes on any two adjoiningslices are aligned with respect to each other so as to define a conduitbetween them. A transmission medium is within the holes.

Another aspect of the invention involves a method of making a fiberoptic connector adapted to receive a fiber bearing unit. The methodinvolves coupling at least two high precision pieces together, the atleast two high precision pieces having holes configured with an opticalmedium inserted therein after the coupling and cured to form a waveguidestructure, coupling the at least two high precision pieces to a lowprecision piece to form a unit, and housing the unit within a fiberoptic connector housing.

A further aspect of the invention involves a communications assemblycomponent has a fiber bundle having a first end and a second endopposite the first end. A first connector is on the first end. A secondconnector is on the second end. The first connector includes a waveguidecomponent having several slices piled together to form a stack. A firstof the slices in the stack has a first through hole. A second of theslices in the stack has a second through hole. The first and secondslices are separated by at least one additional slice. A waveguidestructure connects the first through hole with the second through hole.The first through hole and the second through hole are displaced fromeach other in at least two dimensions.

These and other aspects described herein, or resulting from the usingteachings contained herein, provide advantages and benefits over theprior art. For example, one or more of the many implementations of theinventions may achieve one or more of the following advantages orprovide the resultant benefits of: ease of insertion of a large formatfiber bundle into a large format ferrule, high yield, rapid insertion offibers into connectors, low cost assembly, high precision (fiberplacement to 1 micron or sub micron accuracy), control of fiber pitchduring insertion so that single mode fibers can be easily aligned,controlled placement of multiple fibers at a desired pitch, designscalability, application scalability, integration into standardcommercial connectors, compatibility with commercial connectorthrough-hole pin-placement, manufacturability in a mass-production waferscale process, compatibility with the thermal coefficient of expansionof silicon chips used for transmission and reception of data, lowermaterial cost, lower labor cost, high two- and three-dimensionalaccuracy (since the holes in the array can be placed with lithographicprecision), pieces can be stacked arbitrarily and/or large numbers tomake waveguides which change in two- or three dimensions along theirlength, collimated couplers, optical routers, etc . . . , individualwafer thickness is irrelevant so cheaper, less controlled material canbe used, stacking on a wafer basis rather than on a piece basis to allowfor integration on a massive scale, and/or the ability to use opticalepoxy rather than threaded optical fibers, as used in V-Groovetechniques.

The advantages and features described herein are a few of the manyadvantages and features available from representative embodiments andare presented only to assist in understanding the invention. It shouldbe understood that they are not to be considered limitations on theinvention as defined by the claims, or limitations on equivalents to theclaims. For instance, some of these advantages are mutuallycontradictory, in that they cannot be simultaneously present in a singleembodiment. Similarly, some advantages are applicable to one aspect ofthe invention, and inapplicable to others. Thus, this summary offeatures and advantages should not be considered dispositive indetermining equivalence. Additional features and advantages of theinvention will become apparent in the following description, from thedrawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of a commercial connector assembly;

FIG. 2 shows an example connector hole and fiber;

FIG. 3 shows fibers not centered within holes of FIG. 2;

FIG. 4A shows a one-dimensional fiber array having fibers placed inV-Grooves etched into a piece of silicon;

FIG. 4B shows a stack of two one-dimensional fiber arrays of FIG. 4A;

FIG. 4C shows a hypothetical large format stack of three one-dimensionalfiber arrays of FIG. 4A;

FIG. 5 shows an example of a low-precision piece in accordance with theinvention;

FIG. 6 shows an example of a low-precision piece that is also part highprecision piece;

FIG. 7 shows an example wafer created using one variant of the techniquedescribed herein;

FIG. 8, shows a silicon wafer created using another variant of thetechnique described herein;

FIG. 9 shows a silicon wafer created using another variant of thetechnique described herein having a feature for accurate alignment ofthe wafer relative to another wafer and/or holding of the wafer;

FIG. 10A shows an example high precision piece made using one variant ofthe technique described herein;

FIG. 10B shows an example high precision piece incorporatingmicrolenses, made using another variant of the technique describedherein;

FIG. 11 shows a high-precision piece set up to mount flush on a face ofa low-precision piece;

FIG. 12 shows a tapered piece having a potentially large angle ofinsertion;

FIG. 13 shows one approach to ensuring that an angle of insertion isminimized;

FIG. 14 shows a second approach to ensuring that an angle of insertionis minimized;

FIG. 15 shows a third approach to ensuring that an angle of insertion isminimized;

FIG. 16 shows a variant comprising two high precision pieces and achamber;

FIG. 17 shows another variant comprising two high precision pieces and achamber;

FIG. 18 shows one hole for a high-precision piece superimposed over anoptical fiber;

FIG. 19 shows two fiber holes of the same size as in FIG. 18 ondifferent high precision pieces according to a variant of the invention;

FIG. 20 shows the holes of FIG. 19 holding the optical fiber of FIG. 18where the offset is equally divided between both pieces;

FIG. 21 shows one example of a three piece holder approach;

FIG. 22A shows four wafer pieces or slices with a two dimensional arrayof holes in the center of each slice;

FIG. 22B shows the wafer slices of FIG. 22A in stacking order;

FIG. 22C shows the stack of FIG. 22B being aligned on alignment pins;

FIG. 22D shows the stacked wafer slices of FIG. 22C connected to form ahigh precision waveguide piece;

FIG. 23 shows a series of semiconductor wafer pieces fabricated withholes nearly the same size along with cutaway views of two variantsthereof;

FIG. 24 shows one example tapering waveguide variant;

FIG. 25 shows an example of a two dimensional array of optical Ybranches created using one variant of the techniques described herein;

FIG. 26A shows a more complex, combination application of the techniquesdescribed herein;

FIG. 26B shows a microlens array stacked with two high precision piecesand a low precision piece to create an ferrule compatible with an MTP,MPO, MPX or SMC style connector;

FIG. 26C shows a single optical device focussing light between a deviceand a single mode fiber using the arrangement of FIGS. 26A and 26B;

FIG. 27 is a photograph of a high precision piece created according toone variant of the techniques described herein;

FIG. 28 is a photograph of the piece mounted in a low precision piece asdescribed herein showing the alignment pins;

FIG. 29 is a photograph, in ¾ view of a ferrule for use in an MTPconnector superimposed against a penny; and

FIG. 30 is a photograph of a fully assembled MTP connector as describedherein having 72 light carrying fibers.

DETAILED DESCRIPTION Overview

In overview, the technique uses one or more high-precision pieces thatcan be combined with a low precision piece to form a ferrule-like unitand then integrated into a commercial connector as the ferrule theconnector is designed to receive.

Low Precision Piece Creation

An example of a low-precision piece 500 is shown in FIG. 5. As shown,this particular shape piece is designed in the shape of a ferruleopening in an industry standard connector apparatus so it can beinserted into a commercial connector, for example, in place of theferrule 102 of FIG. 1. In practice, this currently means the pieceshould typically be shaped to dimensionally fit into at least one of anMTP or MPO or MPX or SMC style connector. Depending upon the particularvariant, the low-precision piece 500 is manufactured by, for example, apolymer molding technique, for example, injection molding, transfermolding, or by some other molding, milling or forming technique. In somevariants, the material used for injection molding is a glass filledepoxy, although other epoxies or plastics can be used. Alternatively, inother variants, the material is either metal or some other moldable ormillable material.

The low-precision piece is manufactured to the outer dimensions to allowit to be properly inserted into the desired connector. In addition, ittypically has an opening 502 that is large enough to receive the highprecision piece(s).

In some variants, the “low precision” piece may also be, in part, a highprecision piece, for example, as shown in FIG. 6, if the low precisionpiece 600 is made out of metal and has a thin face 602 that can beprocessed with holes 604 as described below. However, it is expectedthat such variants will lack many of the advantages of using separatelow- and high precision pieces, but may achieve other advantages orbenefits due to the particular application it is being used for or in.

High Precision Piece(s) Creation

By way of representative example, the technique for creating thehigh-precision piece(s) will now be described using a wafer of siliconas the starting point.

While in some variants, silicon is used as the starting material forforming the high-precision piece(s), in other variants, materials suchas ceramics, glass, other insulators, other semiconductor wafercompounds, polymers such as polyimide, or metals, such as aluminum ortungsten or alloys, can be used.

The overall manufacturing process for the high-precision piece(s)proceeds as follows:

a) The wafer is processed into a series of chips by etching holesthrough the wafer using either an etching or drilling process. In somevariants, this is done through a semiconductor lithography processcombined with an etching technique. In other variants, laser drilling isused. The holes are each of specific sizes and, where appropriate,axially offset at a specific angle relative to the plane of the wafer(or piece once cleaved). Features such as holes for alignment pins orbumps and recesses for precision mating are also created, whereappropriate. The wafer contains many copies the chips that will beneeded to make a particular high precision piece, for example, fiberholding piece, a collimator, many-to-one taper or Y branch. The piecesto build up an element of a particular type can be processed on a singlewafer or by making several wafers, each having some of the pieces neededto make the component. In either case, the resultant wafer scale batchprocessing is the same and saves costs.

The holes are classified into two groups: those which are made for fiberinsertion and/or receiving an optical epoxy, and those that are foralignment and/or placement into a connector. Although in the ideal case,the holes are perfectly cylindrical, frustoconical, obconic or funnelshaped, in practice the holes will only be substantially rightcylindrical, right frustoconical or right funnel shaped. However, thosedeviations, for purposes of the processes described herein, areconsidered negligible since they are either a) much smaller than theoptical fiber diameter and hence have no meaningful effect on placementor performance in the case of fiber holding embodiments, or virtuallyirrelevant in the case of waveguide embodiments.

In addition, for the variants described herein, to facilitate fiberplacement or create certain waveguide arrangements, in some cases it maybe desirable to intentionally use cylindrical, frustoconical, obconic orfunnel shaped holes that have a substantially oval, substantially eggshaped or substantially elliptical cross section perpendicular to theiraxes (i.e. they are not round). In other variants, use of somecombination of

FIG. 7 shows an example wafer 700 created using one variant of thetechnique described herein. Each piece 702 (also called a slice)contains a central group of small holes 704 (in this case 72 per piece)for fibers and larger holes 706 on the left and right sides of eachpiece for alignment of the piece relative to some other piece.Typically, the number of holes will be equal to or some multiple of thenumber of fibers in a commercial optical fiber bundle, for example,bundles of 6, 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132 or 144fibers.

FIG. 8, shows a silicon wafer 800 created using another variant of thetechnique described herein. As shown in FIG. 8 , there are small holes802 in each piece 804 within the central area of the wafer for fibers oroptical epoxy and large holes 806 near the edge of the silicon wafer foralignment on a wafer basis.

Additionally, or alternatively, the alignment holes can be part of eachpiece and specifically be spaced so that the piece may be inserted intoan MTP, MPO, MPX, or SMC or other widely available style commercialconnector, such as shown in FIG. 1, as part of or in place of a ferruleand also aligned using alignment pins 110 that are on a part of theconnector itself.

Additionally, other holes or features may be etched into the piece toallow the insertion of epoxies, solder, or some other fastening agent tohold the piece to the low precision piece or so that two or more of thepieces can interlock with each other.

Depending upon the particular variant, in some cases, one or more of thealignment holes on one or more of the components may optionally have anoblong or oval shape to allow some freedom of movement.

Depending upon the particular variant, the particular holes may havestraight or tapered sidewalls.

In some variants using straight holes, the holes are created by laserdrilling. In other variants, the straight holes are formed using anetching process, for example, anisotropic hole etching. By way ofexample, for a silicon wafer, anisotropic deep/via hole etching ofsilicon is performed by photoresist patterning the wafer according tothe desired hole placement and etching using the Bosch process in ahigh-density plasma reactor such as either an electron cyclotronresonance (ECR) or inductively coupled plasma (ICP) reactor. The Boschprocess is based off of a time multiplexing scheme separating the etch(SF6) and passivation (C4F8 sidewall protection) cycles. The etch causesscalloping on the silicon sidewalls and sharp edges at the base of thevia but the profile produces nice straight holes/vias. Since thescalloping creates edges are too sharp for fiber insertion without aguiding structure to help the fiber avoid the edges at the base of thestructure clean-up etching is required.

Both the clean up etching process and the process of creating taperedholes is essentially the same. In addition to the Bosch process, forclean up and creating tapered holes, an isotropic (non-directional)silicon wet etch (HF:HNO₃, 1:1) is used. This produces smooth, damagefree tapered surfaces. In addition, the isotropic wet etch eliminatesand/or reduces the scalloping and sharp edges created from the Boschprocess, making fiber insertion easier and more reliable.

Alternatively, holes/vias can be made with a combination of etching withKOH and the Bosch process. Both KOH etching and Bosch process etchingare well understood and used widely. Etching of silicon using KOH isalso well known and is used in the micro-machining industry and themicro electro mechanical systems (MEMS) area.

In the alternative variants, a Bosch etch is used on the front side ofthe (100) silicon wafer. Then a SiN_(x) stop layer for the KOH isdeposited in the Bosch etched front side hole. The back side of thewafer in then photoresist patterned in alignment with the front side ofthe silicon wafer. The back side is then wet etched with KOH. TheSiN_(x) is then removed. The scalloping and sharp edges are thensmoothed with HF:HNO₃, (1:1). This process produces a via hole that isboth sloped and anisotropic with a sidewall profile that facilitatesfiber insertion.

The process is similar to create the pieces using other materialsexcept, the specific etch process used will differ based upon theparticular material being used. Since techniques for etching and/ordrilling of holes in other materials such as ceramics, glass, otherinsulators, other semiconductor wafer compounds, polymers such aspolyimide, or metals, such as aluminum or tungsten or alloys are allpresently known and can be applied in a straightforward manner basedupon the teachings contained herein, the specific details of performingsimilar/analogous operations, on the other materials, are omitted forbrevity.

In addition, by optionally orienting the wafer during the etchingprocess and using a dry etching processes, it is possible to etch theholes in a preferred direction or at a specified angle. This isdesirable since a controlled angled insertion allows higher efficiencycoupling into single mode fibers (i.e. non-tapered holes can be etchedat a specified angle, for example, an angle up to about 8 degrees withrespect to a perpendicular to the wafer surface, and thus allow insertedfibers to be accurately held precisely at the specified angle). Thisallows a ferrule for single mode fiber to be easily and inexpensivelycreated.

b) Depending upon the wafer material's refractive index, the waferand/or the holes can optionally be coated with a thin layer of metaldeposited, for example, by such techniques as sputtering, evaporation,electroplating or electroless plating.

c) Portions of the wafer may also optionally have a dielectric, solderor other adhesive deposited on it, for example, by surrounding some ofthe holes with a ring of reflowable solder a few microns thick or usingdeposition techniques such as sputter deposition.

d) In some variants, the wafer is then diced into individual pieces. Inother variants, for example, in a batch manufacturing process, the wafermay not be diced until after any of e), f), g), h) or i) below dependingupon the particular wafer, type of arrangement being created or othermanufacturing reasons irrelevant to understanding the invention.

e) The wafers or individual wafer pieces are stacked onto alignmentpins.

Depending upon the particular application differing methods will be usedfor alignment, for example, holes 802 can be placed for alignment on awafer basis (as shown in FIG. 8), rather than on an individual piecebasis. Alternatively, instead of using alignment pins, on a wafer ofpiece basis, a wafer 900 can have some other feature, for example, anotch 902 and/or flattened portion 904 such as shown in FIG. 9 foraccurate alignment and/or holding of the wafer. In some variants, othertechniques for alignment can be used, such as, putting the pieces into aholding jig or using interlocking complementary features etched intoeach piece.

f) The wafers or individual wafer pieces are then fused together, forexample, by heating and melting the solder, which fuses the piecestogether, or by using other bonding techniques including, those usingpressure, adhesives or mechanical devices such as clips, screws orrivets.

g) Optionally, if the holes will not directly hold fibers or hold anelement like a microlens or diffraction grating, optical epoxy and/ordielectric material(s) are flowed and/or sputtered into the holes and,in the case of epoxy, cured to harden it.

h) The alignment pins are optionally removed, and

i) The end faces of the piece are polished to optical quality.

The final piece can also be ground down, prior to, or after, step i), toany specific final shape desired, since the shape of the high-precisionpiece as it goes into the low precision piece can be different from theshape after the pins are removed or the pieces are diced.

It should be noted that the above steps need not be performed inprecisely the order specified. Since the various permutations andcombinations are to numerous to detail, it should be understood that, insome cases, the order can be changed without changing the invention.

Some example variants use a wafer-at-a-time process for creating thehigh-precision pieces in bulk. By making the pieces in wafer form, largenumbers of pieces can be made simultaneously, thus keeping the costsdown. As shown in FIG. 7 over 220 pieces can be made on a single waferat one time. Typically, if an industry standard four inch wafer is used,over 400 pieces for an MTP connector ferrule can be made per wafer.Using an eight inch wafer, allows production of three to four times thatnumber.

Connector Creation

The connector is created by combining the high precision piece(s), thelow-precision pieces, inserting the fibers, and incorporating thecombined piece into the remainder of the connector.

The high precision piece(s) are inserted into a recess in thelow-precision piece and secured, for example, by being epoxied intoplace to hold the pieces together. FIG. 10A shows an example highprecision piece 1000 made of silicon using one variant of the technique.As shown in FIG. 10A, the corners of each high precision silicon pieceare chamfered 1002, specifically at 45 degrees, to allow a region ofspace, between the high precision silicon piece 1000 and the innermostedge of the receiving portion of the low precision piece, for afastening agent. As noted above, other features or holes can be usedalong with or instead of the chamfers for a similar purpose.Alternatively, as shown in FIG. 11 the high-precision piece 1102 can beset up to mount flush on a face 1104 of the low-precision piece 1106.

It is also important to place the high precision piece accurately on orinto the low-precision piece so that the fibers in the connector willalign properly with their counterparts. This can be done, for example,by inserting an alignment piece 106 (such as shown in FIG. 1) containingalignment pins 110 which will protrude through holes 1108 in thelow-precision piece and then through the alignment holes 1110 in thehigh precision silicon piece 1102.

Depending upon the particular connector, the alignment pins can beremoved at this point and not used in any further operation, if they arenot needed or not desired or can remain in, for example, as would be thecase for the MTP connector of FIG. 1. Fibers are inserted through thelow-precision piece and then through the high precision piece so as toterminate in, or just beyond the outer face of the high precision piece.The low-precision piece then is filled with epoxy to hold the fibers inplace via, for example, an inlet formed in the piece. If desired, thecombined unit can then be polished so that the ends of the fibers areflush with the face (i.e. the front) of the combined piece. Optionally,the face of the piece where the fibers are visible can be coated with adiamond thin film (or other hard material) to prevent the silicon frombeing worn down during the polishing process.

Applications

The processes described above for creating the different pieces havenumerous applications. A few will now be described in simplifiedfashion, bearing in mind that more complex arrangements and/orcombinations of the described applications can be readily created usingvariations on the techniques and applications described herein.

Ease of Insertion Variants

Pieces, which have a wide opening on the side where fibers will beinserted while having a narrower opening at the point where the fibersexit, can be used to make fiber insertion easier.

As shown in FIG. 12, a tapered piece 1200 by itself would result in apotentially large angle of insertion “θ” because the fiber will not beconstrained within the piece in a particular position owing to the factthat it can be inserted at an angle, rather than straight in. This isnot desirable since it can cause a loss of light when coupling lightbetween two such connectors or when connecting a fiber bundle to acomponent that emits, detects or routes light.

In order to ensure that the angle is minimized, any of four basicapproaches (or some combination thereof) are used.

Approach 1: Two high-precision pieces 1300, 1302, having taperedsidewalls 1304, 1306 are stacked on top of one another so a fiber 1308has to pass through two narrowing regions (the tapered sidewall holes)which are separated by a space (of typically either the thickness of thelast piece to be passed through or that thickness plus some otherdistance). This is illustratively shown in FIG. 13. Ideally, in such acase, the hole on the side of the piece into which a fiber will first beinserted will have a diameter W and the hole on the opposite side willhave a diameter X, where W>X. Ideally, the diameter X will be close tothe diameter of the fiber, although it will likely be larger. The otherpiece will have a hole, on the fiber entry side, of a diameter Y whichcan be any size equal to, or between, W and X. The exit side of theother piece will have a hole diameter of Z, where Y≧Z.

Approach 2: The two high-precision pieces 1400, 1402 are stacked on topof one another as above, but the first one to be entered by the fiberhas tapered sidewalls 1404 and the other is etched or drilled with“straight” sidewalls 1406 (i.e. they may, or may not, be angled withrespect to a perpendicular to the surface of the piece) so that thesidewalls 1406 in the piece 1402 are approximately ½ the overallthickness of the pieces 1400. 1402 together. The tapered region allowsease of insertion of a fiber 1408 while the straight region maintains alow angle of insertion for a fiber 1408. A longer region of straightsidewalls provides more support and stability for the fiber and thusholds it in place more firmly and without the risk of edge piecesnicking the fiber. This is shown in FIG. 15.

Approach 3: A single high-precision piece 1500 is fabricated in atwo-step process where the piece is etched in a tapered fashion on oneside 1502 and then etched anisotropically on the other side 1504 so thatthe hole on one side of the piece is tapered 1506 while the other sideof the hole in the piece has straight sidewalls 1508 extending withinthe thickness of the piece for approximately ½ the thickness. Thisresults in a single piece (which saves material costs and assembly time)that allows for easy fiber 1510 insertion and a low angle of insertionof a predetermined offset from a perpendicular to the piece for singlemode fibers. This is shown in FIG. 15.

The piece in this approach could be twice as thick as in approaches 1 or2, so as to fit into the same low precision piece. Alternatively, a lowprecision piece specifically designed to accept the piece made usingapproach 3 can be used.

Approach 4: Either two piece approach above is used, but the fiber holesin one or both of the two pieces are made slightly oval, although notnecessarily in alignment with each other. This allows for more flexiblespacing of the guide pin holes to account for inaccuracies in either theguide pins themselves or the guide pin holes, which are sometimes lessaccurate than the fiber holes due to their size.

In still other variants, such as shown in FIGS. 16 and 17, two highprecision pieces 1602, 1604, 1702, 1704 are created as described herein.In addition, a low precision “chamber” 1606, 1706 is also createdbetween the two pieces which can fully surround the fibers (such asshown in FIG. 16), partly surround the fibers (such as shown in FIG.17), or not surround the fibers at all (for example by using precisionstandoffs or spacing posts). In other words, instead of being stackedagainst each other, the high precision pieces 1602, 1604, 1702, 1704will each be separated from each other by the chamber 1606, 1706 or thestandoffs/posts. Individual fibers or a fused tapered one or twodimensional arrayed waveguide structure, either in Y-Branch 1708 orstraight form, is inserted through each of the high precision pieces1602, 1604, 1702, 1704 to create a collimating element, “shuffle”signals passing through the element from one side to the other, orperform a 2 (or more) to 1 mapping of optical devices to optical fibers.Once the fibers are inserted, the high precision pieces 1602, 1604,1702, 1704 are attached to the chamber 1606, 1706 and the chamber orarea around the fibers is filled with an epoxy or other hardening agent.The portions of the fibers extending outside the element are then cutoff, and the exposed faces are polished as noted above. This will allow,for example, a one or two dimensional array of lasers to be coupled ingroups into a separate array of fibers, multiple devices which emit atdifferent wavelengths to be coupled into individual fibers, or multiplelasers at a single wavelength to be coupled into single fibers to allowredundancy during data transmission.

High Accuracy Holding Variants

Two pieces that are designed with commonly aligned fiber holes butalignment holes or other structures that are offset, relative to eachother, can be used to provide greater accuracy in fiber holding thaneither piece can provide alone.

Instead of having the aligning structures in the two pieces in exactlythe same position with respect to the fiber holes, the relationshipbetween the aligning structures and the fiber holes is offset so thatthe fiber holes in the two pieces do not completely line up. FIG. 18shows one hole 1800 for a high-precision piece superimposed over anoptical fiber 1802. Note that the hole is almost 25% larger than thediameter of the fiber. FIG. 19 shows two fiber holes 1900, 1902 of thesame size as in FIG. 18 on different high precision pieces according tothis variant. Instead of the fiber holes being aligned when the piecesare aligned, these fiber holes are offset relative to each other whenthe alignment structures or holes are aligned. The offset isintentionally set at about a predetermined amount, such that the twoclosest parts of the holes are spaced apart by about a fiber diameter.The offset Δ (as shown in FIG. 19), allows two holes which are largerthan a fiber to hold that fiber very accurately since the width of thebiconvex opening 1904 formed by the two pieces, taken along a linepassing through the centers of the holes, is very close to the diameterof the fiber to be placed inside and be closely constrained. Ideally, asshown in FIG. 20, the holes 2000, 2002 are the same size (so the offsetis equally divided between both pieces) so that a single wafer can beused to create one format piece and two identical pieces can be used tohold a fiber 2004 by placing them back-to-back. By way of example, iffor a particular application the fiber holes were, 4 microns too large,offsetting the two pieces by a few microns increases the pitch accuracyfrom a worst-case of 4 microns to as much as a sub-micron accuracy. Thispotentially provides a substantial improvement in coupling efficienciesbetween fibers.

As noted above, elements can be created that combine a high precisionpiece and a low precision piece. Advantageously, if it is possible inthe particular case to make a “low precision” piece with a hole size ofa specified (im)precision but precise offset, then only onehigh-precision silicon piece need be used to hold a fiber with highaccuracy. This further reduces the number of element components fromthree to two. FIG. 11 shows one example of the two piece holder approachand FIG. 21 shows one example of the three piece holder approach usingthe high precision pieces 2100, 2102 having the specified offset Δ and alow precision piece 2104.

The combined pieces can be made in a size and shape that is compatiblewith conventional connectors, for example, the low-precision piece isthe size and outer shape of the conventional ferrule for the connectorof FIG. 1.

Thus, the precision of the fiber hole pitch of the combined unit ishigher than the precision that would be obtained by using orconveniently or cheaply obtainable with any of the individual piecesthemselves.

Waveguide Variants

The high precision pieces need not necessarily be designed to hold afiber. Instead, an arbitrary number of pieces can be created such that,once the pieces are stacked, if the holes are filled with an opticalepoxy a waveguide or collimating element is created.

Such elements are constructed by patterning holes on individual highprecision pieces in an aligned or offset layered fashion and thenstacking those pieces together to form optical routing topologies in thethird dimension. This makes creation of not only simple waveguidestructures possible, but more complicated waveguide topologies,structures to route optical signals through the use of photonic bandgapengineering materials containing periodic structure features throughoutthe material in each of the pieces, or integration of other elements,for example, (by etching or depositing lenses or diffraction gratings inone or more of the pieces. Through creative use of the technique, evenmore complex geometric arrangements or combinations can be achieved.

FIG. 22A shows four wafer pieces 2200, 2202, 2204, 2206 with a twodimensional array of holes 2208, 2210, 2212, 2214 in the center of eachpiece. Note that the holes in each of the arrays of a piece are the samesize, but the different pieces have different size holes with respect toone another. These pieces are then stacked (FIG. 22B) and aligned onrods or pins 2216 (FIG. 22C) so that, when fully integrated, they arepushed together in close contact (FIG. 22D). Once the pieces arestacked, and aligned with respect to one another, the holes are turnedinto an optical guiding medium. This is accomplished by flowing anoptically transparent epoxy into the holes and curing it into a hardenedform. This effectively creates optical fibers inside each of the holes.

In some variants, the walls of the holes are also coated with a metallayer before the epoxy is flowed into the holes.

In other variants, instead of, or in addition to, the metal layer, athin, low dielectric material layer is added on top of the metal priorto flowing the epoxy.

Note that the epoxy or other material which is flowed into the holesneeds to be a higher refractive index than the material which is used toform the walls of the holes. If this is not the case, then the walls ofthe holes in the wafer pieces that will serve as part of the waveguidesare metalized using; for example, electroplating or electroless plating.

FIG. 23 shows a series of semiconductor wafer pieces fabricated 2300,2302, 2304, 2306 with any array of guiding holes, all nearly the samesize. These pieces are stacked on top of one another so that the guidingholes are all aligned. An optical epoxy is flowed through the holes inthe pieces and cured to form the guiding material. Each resultantwaveguide guides light from one end to the other end. As can be seenfrom FIG. 23, a number of pieces can be stacked together to form acollimating element made up of waveguides of arbitrary but controllablelength. For example, if the wafer were 250 microns thick and twelve ofthem are stacked together, a piece 3 millimeters thick would result.

Ideally, if accuracy of alignment can be made high enough, all of theholes should be made perfectly straight to enable a ultra-low-losstransfer of light from one side to the other. However, as will typicallybe the case, if alignment between individual pieces cannot be held totight enough tolerances, each of the pieces can have a tapered hole. Thepieces are then stacked with the smaller end of one piece feeding intothe larger end of the next piece in the direction of expected lighttravel. Thus, if the two pieces are slightly misaligned, the small endwill still allow light to transfer into the next piece through the nextpiece's larger end. In this configuration, it is important that thepieces be arranged so that light will always traverse in the directionfrom the larger ends to the smaller ends to ensure that the maximumamount of light traverses each interface.

FIG. 23 also shows in cross section what one of a series of holes in anarray of holes would look like in a straight sidewalls variant 2308 anda tapered sidewalls variant 2310 after stacking a number of waferpieces. As can be seen, in the example cross sections, thirteen pieceshave been stacked to achieve the resultant shape.

In another variant, by using tapered holes that are intentionallyslightly offset from piece to piece in a particular direction, the holecan direct the light to another location. By using this techniquecreatively, a waveguide can actually “swap” or “shuffle” light amongfibers. For example, with a two fiber connector will mate with anothertwo fiber connector, light leaving fiber 1 will enter the correspondingfiber in the other half of the connector. Advantageously, by using aconnector created as described herein, a stack of high precision piecescan be used to direct the light leaving fiber 1 into the fiber that doesnot correspond when the connectors are joined. This approach can bereadily extended to multiple fibers in the same connector.

In a further variant, the same process is followed, but the holes areall tapered narrower and narrower in each successively stacked piece(i.e. the openings in the first piece are large and the holes in eachsuccessive piece in the stack tapers smaller and smaller).

This allows, for example, a one-dimensional or two-dimensional array ofoptical devices to be coupled to a one dimensional or two dimensionalarray of optical fibers when the number of optical devices exceeds thenumber of optical fibers and hence it becomes desirable to merge thesignals from several optical devices into a single optical fiber. Thisis useful when redundant devices provide for backup signal capability(i.e. one device can operate as the primary device while the otherscoupled into the fiber can be operated as backup devices). Anotherapplication allows several optical devices, each with its own operatingwavelength, to be combined into a single fiber.

There are at least two ways this can be done. One, shown in FIG. 24, isto create a one-dimensional or two-dimensional array of tapers usingmultiple pieces 2400 which when formed into a waveguide combine thelight from a larger area 2402 on one side and taper it down to a smallerarea 2404 on the other side. On the larger end 2402, the opening of thetapered array pieces can have a diameter large enough to accept lightfrom several optical devices simultaneously.

An alternative variant, shown in FIG. 25, the pieces (only two of which2500, 2502 are shown) are designed to be stacked so as to create a twodimensional array of optical Y branches 2504, 2506 which can combine two(or more) optical signals into single fibers. Depending upon theparticular application, the Y branches can be symmetric, asymmetric ordeveloped in random patterns to provide unique connection topologies.

In yet a further variant, by using different sized holes and offsettingthem from piece to piece in the stack the same technique can be used tocombine multiple waveguides into a single waveguide, for example, forcombining the outputs of several optical devices or coupling multipledevices into an individual optical device.

Note that even more complex connections are possible using a similartechnique, for example, 4 to 1 combining arrangements, shuffling ofindividual fiber outputs, combining of non-next nearest neighbordevices, etc. For example, a stack 906 of pieces from the wafer shown inFIG. 9 (stack shown in cutaway cross section not to sacle) creates a 6to 4 to 2 waveguide.

Thus, it should be understood that the technique adds a third dimensionof freedom and thus allows one- or two dimensional arrays of opticaldevices (emitters, detectors, modulators, micro electro mechanicalsystems etc.) to have optical outputs which can be combined, split,routed, and shuffled in an arbitrary manner so that at the output of thestack, signals are output in a specific manner different from the inputto the stack.

In addition, the technique allows for incorporation of other elements,for example, by inserting microlenses 1002 into a high precision piece1004 to create an array of microlenses (FIG. 10B). This can be done by,for example, depositing microlenses in the tapered holes of highprecision pieces such as made in connection with FIGS. 13, 14 or 15 orin etched “stepped” holes of two or more different diameters, or dishedholes (since, in either case, ease of fiber insertion is not a concernfor this piece). Once such a piece is created, it can be integrated withother pieces as desired. Similarly, the approach can be used toincorporate diffraction gratings into a stack or a low precision piece.

The techniques described herein can further be used to create a single,high-density connector to connect fiber riser cables together, insteadof through use of huge multi-connector assemblies as is currently done.

In a further variant, by using a high-precision piece made of silicon ina connector used to attach fiber bundles to transceiver modulescontaining optics attached to semiconductor wafers (e.g. a siliconopto-electronic chip), the thermal coefficient of expansion of the piecein the connector can be readily matched with the coefficient ofexpansion of the chip in the module. Thus the connection will notdegrade appreciably due to temperature fluctuations.

Notably, while some variants of the technique described hereinspecifically use a combination of high-precision and low precisioncomponents, the approach is equally applicable to a single grown,molded, milled, or machined piece that can be processed as either alow-precision, a high precision or combination piece.

FIGS. 26A through 26C show a yet a further, more complex, combinationapplication of the techniques described herein. As shown, a microlensarray 2602, such as shown in FIG. 10B, is incorporated as one of theelements in the stack 2604 of high precision pieces 2606, 2608. As shownin FIG. 26A, fibers 2610, in this case single mode fibers, are held by acombination of a low precision piece 2612 and the two high precisionpieces 2606, 2608. The microlens array 2602 is stacked with the two highprecision pieces and combined with the low precision piece 2612 tocreate, in this case, a ferrule 2614 compatible with an MTP, MPO, MPX orSMC style connector (FIG. 26B). In this application, the connector isdesigned to be coupled to an optical device array 2616, for example, anarray of transmitters 2618. The microlenses 2620 focus the incidentlight beam more narrowly so that more accurate and/or efficient couplingbetween the optical devices and fibers can be obtained.

Advantageously, assuming that the array of devices was created forcoupling to multimode fibers of a particular pitch, through use of theferrule of FIG. 26B, the same array can be coupled to single mode fiberswithout taking any special action or changing the device array at all.FIG. 26C shows a single optical device 2622 in the array 2618 focussinglight 2624 between the device 2622 and a single mode fiber 2626 throughuse of the arrangement shown in FIGS. 26A and 26B.

FIG. 27 is a photograph of a high precision piece 2700 created asdescribed herein.

FIG. 28 is a photograph of the piece 2700 mounted in a low precisionpiece 2800 as described herein and showing alignment pins 2802 passingthrough the low precision piece 2800 and the piece 2700.

FIG. 29 is a photograph, in ¾ view of a ferrule created according to onevariant of the invention, for use in an MTP connector and superimposedagainst a penny for relative sizing.

FIG. 30 is a photograph of a fully assembled MTP style connector asdescribed herein having at least one high precision piece holding 72light carrying fibers.

Thus, while we have shown and described various examples employing theinvention, it should be understood that the above description is onlyrepresentative of illustrative embodiments. For the convenience of thereader, the above description has focused on a representative sample ofall possible embodiments, a sample that teaches the principles of theinvention. The description has not attempted to exhaustively enumerateall possible variations. That alternate embodiments may not have beenpresented for a specific portion of the invention, or that furtherundescribed alternate embodiments or other combinations of describedportions may be available, is not to be considered a disclaimer of thosealternate embodiments. It can be appreciated that many of thoseundescribed embodiments are within the literal scope of the followingclaims, and others are equivalent.

1. An apparatus for use in a commercial fiber optic connectorcomprising: an assembly of a set of slices, each of the slices havingmultiple through holes of a specified arrangement; at least some of thethrough holes on any two adjoining slices being aligned with respect toeach other so as to define a conduit between the any two adjoiningslices; a transmission medium within the holes; and wherein some of theat least some through holes on the any two adjoining slices are axiallymisaligned with each other.
 2. An apparatus for use in a commercialfiber optic connector comprising: an assembly of a set of slices, eachof the slices having multiple through holes of a specified arrangement;at least some of the through holes on any two adjoining slices beingaligned with respect to each other so as to define a conduit between theany two adjoining slices; a transmission medium within the holes;wherein the at least some through holes have straight sidewalls; andwherein, when a cross section of the assembly is taken along a throughhole axis, a group of the through holes collectively comprise a Ybranch.
 3. An apparatus for use in a commercial fiber optic connectorcomprising: an assembly of a set of slices, each of the slices havingmultiple through holes of a specified arrangement; at least some of thethrough holes on any two adjoining slices being aligned with respect toeach other so as to define a conduit between the any two adjoiningslices; a transmission medium within the holes; wherein the at leastsome through holes have straight sidewalls; and wherein at least twothrough holes on a first slice are aligned with a single common throughhole on a second adjoining slice.
 4. An apparatus for use in acommercial fiber optic connector comprising: an assembly of a set ofslices, each of the slices having multiple through holes of a specifiedarrangement; at least some of the through holes on any two adjoiningslices being aligned with respect to each other so as to define aconduit between the any two adjoining slices: a transmission mediumwithin the holes; wherein the at least some through holes have taperedsidewalls; and wherein, when a cross section of the assembly is takenalong a through hole axis, a group of the through holes collectivelycomprise a Y branch.
 5. An apparatus for use in a commercial fiber opticconnector comprising: an assembly of a set of slices, each of the sliceshaving multiple through holes of a specified arrangement; at least someof the through holes on any two adjoining slices being aligned withrespect to each other so as to define a conduit between the any twoadjoining slices; a transmission medium within the holes; wherein the atleast some through holes have tapered sidewalls; and wherein at leasttwo through holes on a first slice are aligned with a single commonthrough hole on a second adjoining slice.
 6. An apparatus to guide lightbetween an optical device and a fiber comprising: a set of pieces, eachcleaved from a silicon wafer having a first side and a second side,wherein each piece has internal walls defining a two-dimensional arrayof holes created by: i) performing a Bosch etch on the first side of thesilicon wafer to create etch indentations in the silicon wafer, ii)depositing a SiNX stop layer in the etch indentations; iii) photoresistpatterning the second side in alignment with the indentations in thefirst side, iv) wet etching the second side, and v) removing the SiNXstop layer, the pieces being stacked together as a unit such that thefirst sides abut the second sides, and at least some of the holes in onepiece at least partly align with at least some of the holes in anabutting piece, and the pieces having an optical transmission mediuminside at least some of the holes.
 7. The apparatus of claim 6 theapparatus is further created by vi) performing a clean up etching of theholes.
 8. The apparatus of claim 6 further comprising: at least onealignment hole in each piece in the stack.
 9. A coupler, of dimensionssuitable for use in a commercial fiber optic connector adapted to accepta ferrule, the coupler comprising: multiple pieces each having athickness and edges defining a first surface and a second surfaceopposite the first surface, the pieces each further having an array ofholes, at least some of the holes being guide holes extending throughthe thickness between the first surface and the second surface, the atleast some guide holes having a first opening size on the first surfaceand a second opening size on the second surface smaller than the firstopening size, the multiple pieces being joined in a stack anddimensioned so as to fit within the commercial fiber optic connector asat least part of the ferrule, and the guide holes each being filled withan optical epoxy.
 10. The coupler of claim 9 wherein the second openingsize is substantially constant for a distance within the thickness. 11.The coupler of claim 10 wherein the distance is approximately ½ of thethickness.
 12. The coupler of claim 10 wherein the transition betweenthe first opening size and the second opening size is substantiallylinear.
 13. The coupler of claim 9 wherein the distance is approximatelyequal to one of a four inch silicon wafer thickness or an eight inchsilicon wafer thickness.
 14. The coupler of claim 9 wherein: a firstpiece in the stack abuts a second piece in the stack, a guide hole onthe first piece is coaxial with a guide hole on the second piece, andthe optical epoxy provides an optical path between the guide hole on thefirst piece and the guide hole on the second piece.
 15. The coupler ofclaim 9 wherein: a first piece in the stack abuts a second piece in thestack, a guide hole on the first piece has a first axis, a guide hole onthe second piece has a second axis, the optical epoxy provides anoptical path between the guide hole on the first piece and the guidehole on the second piece, and the first axis and the second axis are notaligned.
 16. The coupler of claim 9 wherein the stack comprises exactlytwo pieces.
 17. The coupler of claim 9 wherein the stack comprises atleast three pieces.
 18. The coupler of claim 9 wherein the stackcomprises at least 10 pieces.
 19. The coupler of claim 9 furthercomprising a low precision unit adapted to receive the stack, the lowprecision unit having a peripheral surface shaped like the ferrule. 20.The coupler of claim 9 wherein the commercial fiber optic connector isone of an MTP, MPO, MPX or SMC type connector and wherein the couplercomprises a low precision unit adapted to receive the stack and thestack, the low precision piece and the stack when combined havingdimensions substantially equal to a respective one of an MTP, MPO, MPXor SMC ferrule dimensions.
 21. A method of making a fiber opticconnector adapted to receive a fiber bearing unit, the methodcomprising: coupling at least two high precision pieces together, the atleast two high precision pieces each having a two-dimensional array ofholes and configured with a curable optical medium inserted thereinafter the coupling and cured to form a waveguide structure, coupling theat least two high precision pieces to a low precision piece to form aunit, and housing the unit within a fiber optic connector housing.
 22. Acommunications assembly component comprising: a fiber bundle having afirst end and a second end opposite the first end, a first connector onthe first end, the first connector comprising a waveguide componenthaving several slices piled together to form a stack, a first of theslices in the stack having a first through hole, a second of the slicesin the stack having a second through hole, the first and second slicesbeing separated by at least one additional slice, a waveguide structureconnecting the first through hole with the second through hole, thefirst through hole and the second through hole being displaced from eachother in at least two dimensions.
 23. The communications assemblycomponent of claim 22 wherein the at least two dimensions are exactlythree dimensions.